# 2517. Switching Lights

Farmer John tries to keep the cows sharp by letting them play with

intellectual toys. One of the larger toys is the lights in the barn.

Each of the $N (2 \leqslant N \leqslant 500)$ cow stalls conveniently numbered 1~ $N$ has a colorful light above it.

At the beginning of the evening, all the lights are off. The cows control the lights with a set of N pushbutton switches that toggle the lights; pushing switch i changes the state of light i from off to on or from on to off.

The cows read and execute a list of $M (1 \leqslant M \leqslant 2,000)$ operations expressed as one of two integers $(0 \leqslant operation \leqslant 1)$.

The first operation (denoted by a 0 command) includes two subsequent integers $S_i$ and $E_i (1 \leqslant S_i \leqslant E_i \leqslant N)$ that indicate a starting switch and ending switch. They execute the operation by pushing each pushbutton from $S_i$ through $E_i$ inclusive exactly once.

The second operation (denoted by a 1 command) asks the cows to count how many lights are on in the range given by two integers $S_i$ and $E_i (1 \leqslant S_i \leqslant E_i \leqslant N)$ which specify the inclusive range in which the cows should count the number of lights that are on.

Help FJ ensure the cows are getting the correct answer by processing the list and producing the proper counts.

### 输入格式

• Line 1: Two space-separated integers: $N$ and $M$

• Lines 2 ~ M+1: Each line represents an operation with three space-separated integers: operation, $S_i$, and $E_i$

### 输出格式

• Lines 1 ~ number of queries: For each output query, print the count as an integer by itself on a single line.

### 样例

Input
4 5
0 1 2
0 2 4
1 2 3
0 2 4
1 1 4
INPUT DETAILS:
Four lights; five commands. Here is the sequence that should
be processed:
=========Lights
=========1 2 3 4
Init:====O O O O , O = off * = on
0 1 2 -->* * O O ,toggle lights 1 and 2
0 2 4 -->* O * *
1 2 3 -->1 ,count the number of lit lights in range 2..3
0 2 4 -->* * O O ,toggle lights 2, 3, and 4
1 1 4 -->2 ,count the number of lit lights in the range 1..4

Output
1
2


167 人解决，232 人已尝试。

209 份提交通过，共有 438 份提交。

2.8 EMB 奖励。